The present invention relates generally to apparatus and methods for coupling driving and driven mechanisms during operation thereof, and more particularly provides pneumatically powered disconnect apparatus uniquely operable to very rapidly decouple an engine from a driven accessory without imposing appreciable rigid impact force upon the disconnect apparatus, the engine or the accessory.
A wide variety of disconnect devices have heretofore been employed to uncouple driving mechanisms, such as engines, from accessory devices which they customarily rotationally drive by means of a connecting shaft slidably coupled at its opposite ends to the engine and accessory. However, especially in high speed applications, conventional disconnect devices present one or more of several well known problems and disadvantages.
One such problem is a rather complex disconnect structure requiring the use of a fairly large number of high strength parts which must precisely cooperate to reliably effect the desired high speed disconnection of the shaft from one of the coupled mechanisms. The previously necessary structural complexity increases the manufacturing, assembly and maintenance time and cost of such disconnect devices, as well as increasing the number of potential failure points therein.
Another shortcoming inherent in conventional disconnect devices is the necessity of imposing rigid impact forces upon their components to initiate and terminate the uncoupling motion of the shaft which drivingly connects the engine and accessory. As an illustration of this "hardware impact" problem, in one very common disconnect system the connecting drive shaft is splined at its opposite ends and is slidably coupled to the engine and accessory so that axial movement of the shaft will cause its disconnection from one of them. A nut member having a radially outwardly projecting stop portion thereon is threadedly mounted on an intermediate portion of the shaft and rotates therewith under normal operating conditions.
To disconnect the shaft, a pin or other rigid element is moved into the path of the rotating stop portion. The stop portion slams into the pin and instantly stops the rotation of the nut member. The shaft, still rotationally driven by the engine, axially advances itself at a rapid rate relative to the stationary nut member to uncouple the engine and accessory. Subsequent to uncoupling, a portion of the shaft is driven against an abutment on the disconnect to abruptly terminate the shaft's axial motion.
These high speed disconnect component impacts limit the reusability of conventional disconnect apparatus. For example, in disconnects of the "drop pin" type just described, the pin is subjected in high speed applications to very high stress levels which can shear or deform it after only a few uses (or during its first use). After such damage the disconnect must be repaired or replaced.
In another common disconnect design, separate portions of the drive shaft are connected by a linking member purposely designed to be broken (by other components of the disconnect mechanism) when disconnection is desired. This, of course, negates the possibility of reusing or resetting the mechanism. It is only good for one use. Additionally, there is always the concern that the drive shaft's weak link will unexpectedly break of its own accord, leaving the engine-accessory system inoperative until the one-use disconnect system is rebuilt. In a great many applications, this situation is simply unacceptable.
It can be seen that there is a need for a reusable, high speed engine-accessory disconnect system which has a reduced number of components, operates without imposing appreciable impact forces on such components, and is easily and quickly resettable. Accordingly, it is an object of the present invention to provide such disconnect apparatus , and associated methods, and thereby eliminate or minimize above-mentioned and other problems and disadvantages associated with previous disconnect systems.